Actuating device

ABSTRACT

An actuating device for regulating a control mechanism which is subject to a force against the direction of regulation. The actuating device includes a drive device which has a drive shaft and is connected in a moveable manner to a rotating spindle, by which means an actuating element can be axially displaced in the direction of regulation, in a housing receiving the device. The aim of the invention is to improve one such actuating device in such a way that actuation of the control mechanism is guaranteed in a constructively simple and cost-effective manner. In order to achieve this, the drive device comprises at least two electric motors which can respectively be actuated and controlled for the rotation of the drive shaft.

BACKGROUND OF THE INVENTION

The invention relates to an actuating device for regulating a controlmechanism which is subjected to a force against the direction ofregulation. Said actuating device comprises a drive device which has adrive shaft and is connected in a moveable manner to a rotating spindle,by which means an actuating element can be axially displaced in thedirection of regulation, in a housing receiving the device.

Such an actuating device is, for example, known from EP 1 024 422. Suchactuating devices are used especially for regulating control devicessuch as valves, throttle devices and other control mechanisms,especially in applications in oil and gas production. The actuatingdevice is used for maritime and terrestrial locations which may beremote or have difficult access. By displacing the actuating elementusing the rotating spindle, a valve, for example, is closed orappropriately opened as a control device. Generally in this connection,such a valve is subjected to a force in the direction of the openposition, produced by a spring element or similar. To regulate therotating spindle, it is connected in a movable manner to a drive shaftwhich is driven by a drive device for regulating the rotating spindleand correspondingly the actuating element in the regulation direction.The actuating device comprises a device housing in which essentially allparts of the actuating device are accommodated and protected againstharsh ambient effects in appropriate regions of deployment of theactuating device.

Generally, the point of use of such actuating devices is positionedremotely to the associated monitoring and motor control device andadditionally it is usually difficult to access, such as for example,with maritime oil and gas production in which the actuating device andthe associated control device are located on the sea bed. In order to beable to operate the control device even during a failure or withinsufficient effect from the actuating device, a second independentactuating device can be assigned to the same control device. This meansthat with the failure of one actuating device the other one is employedand remotely operated appropriate to the actuation of the controldevice.

The constructive complexity and financial cost for the arrangement oftwo actuating devices for only one control device is quite high. Inaddition, in this case both actuating devices must be maintained andinstalled at the location of use, whereby often insufficient space isavailable.

The object of the application is therefore to improve an actuatingdevice of the type mentioned at the beginning such that actuation of thecontrol device is ensured in a constructively simple and less expensivemanner.

U.S. Pat. No. 4,179,944 shows an actuating device with a drive shaft fordriving a throttle. The drive shaft is arranged displaceable within aguide sleeve, whereby suitable balls are provided between these two as abearing. The drive shaft can be withdrawn by rotating a motor and fedforward by rotating a second motor. Appropriate armature windings areprovided for both motors and an additional device for fixing a spindlenut is provided between the motors.

In the normal operating mode the armature windings of the motors areseparate from one another, whereby a suitable locking pin engages thespindle nut. With the occurrence of a fault, one motor rotates in theclockwise direction and the other motor in the counter-clockwisedirection so that the corresponding armature windings move towards oneanother to move the locking pin into a release position. Then, thespindle nut can move in the longitudinal direction of the drive shaft.

Accordingly, both motors are not used to mutually substitute oneanother, to move the drive shaft in both directions of rotation or,should the occasion arise, to drive the drive shaft together in bothdirections of rotation.

The object of the application is therefore to improve an actuatingdevice of the type mentioned at the beginning such that actuation of thecontrol device is ensured in a constructively simple and less expensivemanner.

BRIEF SUMMARY OF THE PREFERRED EMBODIMENTS

The object is solved according to the invention in that the drive devicecomprises at least two independent electric motors which canrespectively be actuated and controlled for the rotation of the driveshaft.

Through the use of at least two electric motors it is ensured that withthe failure of one motor the other one continues to drive the driveshaft in order to move the rotating spindle and the actuating elementappropriately in the regulating direction. All other parts of theactuating device are present in the usual numbers and only the number ofelectric motors is doubled. According to the invention, a second driveshaft is also not needed on which the second electric motor acts andthrough which it controls the rotating spindle and actuating element. Asa consequence, overall the actuating device according to the inventionis in its dimensions essentially unchanged with respect to thepreviously known actuating device. Alternatively, both motors are usedsimultaneously, if, for example, a higher driving force is needed.

An especially simple and space-saving arrangement can be seen in thatthe electric motors are arranged one behind the other in thelongitudinal direction of the drive shaft.

In order to be able to control each of the electric motors individuallyand essentially independently of one another, a dedicated motor controldevice can be assigned to each motor. The said motor control devicecontains a suitable microprocessor, memory devices and similar devices.Each of the electric motors can be operated according to requirementsthrough an appropriate software program using the microprocessor.

In order to achieve a very accurate motion control with high reliabilityand high efficiency of the electric motors, the said motors can berealized as servomotors.

In order to obtain a bearing mechanism of high quality and highefficiency which is at the same time reversible in its movement in asimple manner, a rotating sleeve can be driven by a drive shaft via atransmission device, the said rotating sleeve being rotationally rigidlyconnected to a ball nut of a feed device, whereby the rotating spindleformed as a recirculating ball spindle for movement in the regulatingdirection is rotationally supported in the ball nut. In this way thedrive force of the electric motors is transferred to the ball nut viathe rotating sleeve. The said ball nut rotates together with therotating sleeve and with the suitable rotation the recirculating ballspindle is moved in the regulating direction and consequently also theactuating element. It is also possible that instead of the previouslydescribed ball screw drive a roller screw drive is analogously applied.

In order to prevent reactions by the control device, which is subjectedto force in the direction opposite to the regulating direction, via theactuating element and rotating spindle or recirculating ball spindle onthe electric motors, the rotating sleeve can be fixed by a first spiralspring opposing a feed rotational direction on a ring flangerotationally rigidly arranged in the device housing. The feed rotationaldirection corresponds here to a rotation of the recirculating ballspindle for the regulation of the actuating element or the rotatingspindle in the regulating direction.

A constructively simple way of arranging such a ring flange can be seenin that the said ring flange sticks out from a transverse wall in thedevice housing essentially coaxially to the drive shaft or to therotating sleeve.

In order to enable resetting of the actuating element in the directionopposing the regulating direction despite this when the control of theactuating device fails, a retaining sleeve can be rotationally rigidlyconnected at one of its ends to the transverse wall, whereby theretaining sleeve is rotationally rigidly connected at its other end viaa second spiral spring to a guide sleeve in the direction opposite tothe feed rotational direction, the actuating element connected to therecirculating ball spindle being supported for longitudinaldisplacement, but rotationally rigidly in the said guide sleeve. If thissecond spiral spring is released during a failure of the usuallyprovided control for the actuating device, the guide sleeve can rotatein the direction opposite to the feed rotational direction due to theforce which is transferred via the actuating element and which is actingon the control device to be actuated. Through this rotation the rotatingspindle is turned back in the recirculating ball nut also in thedirection opposite to the regulating direction until the actuatingelement is again arranged in its initial position.

In this connection, in order to prevent the actuating element itselffrom being rotated in the direction opposite to the regulating directionwhen being displaced, a spindle head for mutual connection can bearranged between the said actuating element and the recirculating ballspindle. The actuating element is decoupled with regard to rotation fromthe recirculating ball spindle by this spindle head.

In order to enable appropriate guidance and retention with regard to theguide sleeve as mentioned above, the spindle head can comprise at leastone guide element protruding radially outwards, which engages alongitudinal guide running in the guide sleeve in the regulatingdirection.

In order to wind up the second spiral spring for the rotationally rigidconnection of the retaining sleeve and guide sleeve sufficiently tightlyon them, the said spring can be drive-connected to at least one electricmotor. A sufficiently rotationally rigid connection between theretaining sleeve and the guide sleeve is produced by suitable actuationof the electric motor for winding up the spiral spring, especiallybefore regulation of the recirculating ball spindle and actuatingelement.

In order to be able to accommodate the appropriate electric motor at aconvenient point within the device housing, the electric motor can bedrive-connected to a clamping sleeve from which a dog protrudes radiallyinwards which can be motion-connected to essentially one end of thesecond spiral spring. Due to the arrangement of the clamping sleeve, theelectric motor can be located remotely with respect to the second spiralspring. Here, the arrangement is preferably realized such that a spaceavailable in the device housing is optimally used.

In order to be able to arrange the actuating device suitably compact andwith small outer dimensions, the clamping sleeve can be rotationallysupported on an external side of the retaining sleeve and on an externalside of a ring flange which engages in the device housing, whereby thering flange protrudes from an inner side of a housing cover.

A simple type of drive connection between the electric motor andclamping sleeve can be seen in that the electric motor drives agearwheel which engages teeth on especially one end of the clampingsleeve.

In order to achieve redundancy also in connection with the drive of theclamping sleeve, another electric motor can be arranged, especiallydiametrically opposed to the first electric motor, through which agearwheel that meshes with the teeth can be driven. In this way theclamping sleeve can be alternatively driven by the first or secondelectric motor and especially with the failure of one electric motor theother one is used.

In order to be able to still release the second spiral spring with thefailure of both electric motors, a torsion spring can be arrangedbetween the clamping sleeve and ring flange, the said torsion springbeing able to be tensed during the rotation of the clamping sleeve forwinding up the second spiral spring. If therefore the clamping sleeve isno longer held by one of the electric motors during the failure of itselectrical supply in such a position in which the second spiral springis wound up, the torsion spring rotates back the clamping sleeve atleast so far that the second spiral spring is relieved for the releaseof the rotationally rigid connection between the retaining sleeve andthe guide sleeve.

In order to be able to finely and accurately control the rotation of theclamping sleeve, the first and second electric motors can be steppermotors.

In order to supply the motors of the actuating device with electricityalso independently of one another at least two separate electricalconnections are arranged on the device housing and especially on thehousing cover adjacent to the electric motors. The appropriate voltagesupply as well as the data interchange or interchange of control signalscan be implemented via these electrical connections. Each of theelectrical connections can be provided for one of the electrical motors,i.e. servomotors. In this connection it is also possible that each ofthe electrical connections is assigned to a stepper motor. A furtherpossibility is also the provision of separate electrical connections forthe stepper motors.

According to the invention, there is the possibility that the twoelectric motors can be controlled independently of one another for theseparate drive of the drive shaft. In this case it is practicable tooperate one of the electric motors in the idling mode when the otherdrives the drive shaft.

However, in order to be able to transfer a higher torque to the driveshaft when necessary and therefore to displace the actuating element inthe regulating direction with a higher force, both electric motors(servomotors) can be operated simultaneously.

In this case, in order to prevent the motors from rotating the driveshaft with a phase displacement due, for example, to different motorcharacteristics or due to the formation of the separate electricalsupply for both motors instead of providing mutual support duringsimultaneous operation, the servomotors can be especially synchronizedby software via their associated motor control devices.

A simple type of synchronization and control can be seen in that oneservomotor is used as the master and the other as the slave.

It can be seen as being advantageous, especially for the transmission ofa high torque if each of the servomotors is a direct current motor.

For the further monitoring of the actuating device according to theinvention, especially remotely from said actuating device, a positionsensor can be assigned to the drive shaft. With the said sensor it canbe found, for example, how far the actuating element has been regulated,whether it has returned to its initial position, etc.

BRIEF DESCRIPTION OF THE DRAWINGS

In the following an advantageous embodiment of the invention isexplained in more detail and described based on the enclosed figures inthe drawing.

The following are shown:

FIG. 1 shows a basic illustration of the actuating device according tothe invention with two separate electric motors and associated controldevice;

FIG. 2 shows a front view of a housing cover of the actuating deviceaccording to the invention;

FIG. 3 shows a cross-section along the line Ill—Ill from FIG. 2, and

FIG. 4 shows a cross-section along the line IV—IV from FIG. 2.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

FIG. 1 shows the basic principle of the actuating device 1 according tothe invention with two separate electric motors 8, 9 as drive device 3.The electric motors 8, 9 are realized as direct current servomotors andare both used, where necessary, independently of one another forrotating a drive shaft 2. As shown in the following figures, when thedrive shaft 2 is rotated, a rotating spindle 4 is displaced in theregulating direction 6 and accordingly an actuating element 5 connectedto it is also displaced. The actuating element 5 is used, for example,for closing or opening a valve as control device (not shown) to beactuated by the actuating device 1.

The servomotors 8, 9 are each electrically connected to a dedicatedmotor control device 11 or 12. These devices comprise appropriately amicroprocessor, a memory device and other components necessary for thecontrol. An appropriate software program for controlling the servomotorsis held in the motor control devices.

Each of the motor control devices 11, 12 can be separately connected tothe actuating device 1 via suitable connections 44, 45 (see for exampleFIG. 2). In addition, each of the motor control devices 11, 12 isconnected to a suitable voltage supply.

FIG. 2 shows a front view of a housing cover 46 of a device housing 7,see FIGS. 3 and 4, of the actuating device 1 according to the invention.The housing cover 46 can also be realized as the end of a subhousing,see FIGS. 3 and 4, which can be releasably connected to the rest of thedevice housing 7.

In the housing cover 46 especially the connections 44, 45 for theelectrical supply and control of the servomotors 8, 9 are arranged. Asmaller cover 48 is arranged centrally with respect to the housing cover46, the said smaller cover covering a pot-shaped protrusion of thehousing cover 46, see again FIGS. 3 and 4, in which a position sensor 47is located.

FIG. 3 shows a section along the line III-IIIl and FIG. 4 shows asection along the line IV—IV from FIG. 2.

In the following the actuating device 1 according to the invention isdescribed based on both of the FIGS. 3 and 4.

The two servomotors 8, 9 of the drive device 3 are arranged in thelongitudinal direction 10 of the drive shaft 2 one behind the other. Thedrive shaft 2 extends adjacent to the position sensor 47. The saidsensor is used to measure rotation of the drive shaft 2 and thereforefor the determination of a feed of the actuating element 5 in theregulating direction 6.

The drive shaft 2 terminates in a transmission device 13, which, forexample, can be realized as a so-called flex-spline gearbox withoutclassical gearwheels. A rotating sleeve 14 is rotated by the drive shaft2 via the transmission device 13, the said rotating sleeve beingrotationally rigidly connected to a ball nut 15 as part of a feed device16. A further part of the feed device 16 is formed by the rotatingspindle 4 which is realized as a recirculating ball spindle.

A spindle head 25 is arranged on one end of the rotating spindle 4 whichprotrudes from the ball nut 15. The actuating element 5 is connected tothe said spindle head on its side opposite the rotating spindle 4. Therotating sleeve 14 is rotationally supported in the ball bearing 49 withrespect to a retaining sleeve 20 which surrounds the rotating sleeve.The rotating sleeve 14 is inserted into a ring flange 18 at its endfacing the transmission device 13.

A first spiral spring 17 is wound up on the outer sides of the ringflange 18 and the rotating sleeve 14. The said spring is used to providethe rotationally rigid connection of the ring flange 18 and the rotatingsleeve 14 in a rotational direction opposite to the feed rotationaldirection of the rotating sleeve 14, i.e. the direction of rotationthrough which both the rotating spindle 4 and also the actuation element5 are displaced in the regulating direction 6.

The ring flange 18 protrudes essentially coaxially to the drive shaft 2,respectively rotating spindle 4 from a transverse wall 19. The said wallis arranged in the region of the device housing 7 where it is releasablyconnected to the subhousing 51.

A retaining sleeve 20 is rotationally rigidly connected to thetransverse wall 19 radially outwards relative to the ring flange 18, seeespecially FIG. 3. The rotationally rigid connection is realized byscrewing one end 21 of the retaining sleeve 20 to the transverse wall19. The retaining sleeve 20 extends up to its end 22 which faces awaythe transverse wall 19. The said retaining sleeve is rotationallysupported relative to a guide sleeve 24 on this said end via a ballbearing 53. A second spiral spring 23 is wound up on the outsides ofboth the retaining sleeve and also the guide sleeve 24.

The guide sleeve 24 extends to a housing cover 36 through which theactuating element 5 is passed. The guide sleeve 24 exhibits longitudinalguides 27 running in the regulating direction 6 and in which guideelements 26 engage. The said guide elements protrude outwards radiallyfrom the spindle head 25.

In the region of the longitudinal guides 27 the guide sleeve 24 isinserted into a ring flange 34 which protrudes from an inner side 35 ofthe housing cover 36. A clamping sleeve 29 is rotationally supported bysuitable bearings on an external side 33 of the ring flange 34 and on anexternal side 32 of the retaining sleeve 20. The clamping sleeve 29 isreleasably connected at its end 39 facing the drive device 3 by screwingto a toothed ring 42. The toothed ring 42 exhibits inner teeth as toothsystem 38 which engages the gearwheels 37, 41. The gearwheel 37 can berotated by a first electric motor 28 and the other gearwheel 41 by asecond electric motor. The electric motors 28, 40 are realized asstepper motors.

A dog 30 protrudes radially inwards approximately centrally to theclamping sleeve 29 and said dog can be coupled to one end 31 of thesecond spiral spring 23, so that, depending on the rotation of therotating sleeve 14, the second spiral spring 23 can be wound up more orless on the retaining sleeve 20 and the guide sleeve 24.

A torsion spring 43 is arranged between the clamping sleeve 29 and ringflange 34. The said spring can be clamped between the ring flange 34 andthe rotating sleeve 14 when the clamping sleeve 29 is rotated forwinding up the second spiral spring 23.

In the following the function of the actuating device according to theinvention is briefly explained based on the enclosed figures.

Since the servomotors 8, 9 are mounted on the drive shaft 2, they can beused singly as well as in combination. Single application occursespecially when one of the servomotors 8, 9 is to replace the other one.Common actuation of both servomotors 8, 9 is especially then providedwhen a higher torque is to be transferred onto the drive shaft 2, whichmay amount to twice the torque which can be transferred by oneservomotor.

Both servomotors 8, 9 are connected via separate feed cables, see theconnections 44, 45, and the partially illustrated connection line 50, totheir respective motor control devices 11, 12. One of the servomotors 8,9, or both motors can be actuated and controlled via these controldevices and separate electrical supplies to the motor control device andalso to the servomotors.

The motor control devices 11, 12 are especially formed in that one ofthe servomotors is wired as the master and the other as the slave andsynchronization of both motors to the common drive of the drive shaft 2occurs by software.

The electric motors 28, 40, formed as stepper motors, are also arrangeddouble in order to substitute one of the stepper motors with failure,damage or a similar condition. Also in this case, the control of thestepper motors occurs independently of one another over dedicated feedcables and dedicated motor control devices.

Otherwise the actuating device according to the invention functions asfollows:

The ball nut 15 is rotated through the rotating sleeve 14 by rotatingthe drive shaft 2. Since the said ball nut is fixed in the axialdirection relative to the device housing 7, the rotating spindle 4 isdisplaced in the regulating direction 6 when the ball nut 15 is rotated.The actuating element 5 is also displaced at the same time as therotating spindle 4, because the said actuating element is connected tothe rotating spindle 4 via the spindle head 25. The displacement of theactuating element 5 can be measured via the position sensor 47.

The force applied to the actuating element from the direction of thecontrol device, which is not illustrated, in the opposite direction tothe regulating direction 6 is transferred via the first spiral spring 17from the rotating sleeve 14 to the ring flange 18 and therefore to thehousing 7.

For resetting the actuating element 5 in the opposite direction to theregulating direction 6, the second spiral spring 23 is released via thedog 30, the said spiral spring holding the guide sleeve 24 with theretaining sleeve 20 rotationally rigid in the direction opposite to thefeed rotational direction. With the second spiral spring 23 released,the guide sleeve 24 can rotate in the direction opposite the feedrotational direction, whereby the rotation onto the guide sleeve 24 istransferred via the guide elements 26 of the spindle head 25corresponding to the reverse rotation of the rotating spindle.

If due to the failure of both stepper motors 28, 40 a release of thesecond spiral spring 23 is not possible, the release of the spiralspring 23 occurs through the torsion spring 43, which was tensed onwinding up the second spiral spring 23 for the rotationally rigidconnection of the guide sleeve 24 and retaining sleeve 20 between theclamping sleeve 29 and the ring flange 34.

1. An actuating device for regulating a control mechanism subjected to aforce against the direction of regulation, whereby the actuating devicecomprises: a drive shaft; a rotating spindle spaced axially apart fromand connected in a moveable manner to said drive shaft; an actuatingelement adapted to be axially displaced by said rotating spindle in thedirection of regulation; at least two electric motors, each motoradapted to be actuated and controlled both individually and inco-operation, each of the at least two electric motors being capable ofrotating said drive shaft in a feed direction; and a housing adapted toreceive the actuating device.
 2. The actuating device according to claim1, wherein said electric motors are arranged one behind the other inboth directions of rotation in the longitudinal direction of said driveshaft.
 3. The actuating device according to claim 1, further comprisinga dedicated motor control device is assigned to each of said electricmotors.
 4. The actuating device according to claim 1, wherein saidelectric motors are servomotors.
 5. The actuating device according toclaim 1, further comprising a rotating sleeve adapted to be driven bysaid drive shaft via a transmission device and rotationally rigidlyconnected to a ball nut of a feed device, wherein said rotating spindleis a recirculating ball spindle and is rotationally supported in theball nut for movement in the regulation direction.
 6. The actuatingdevice according to claim 5, further comprising: a ring flangerotationally rigidly arranged in said housing; and a first spiral springattached to said rotating sleeve and said ring flange so as to preventrotation of said rotating sleeve in a direction opposite the feeddirection.
 7. The actuating device according to claim 6, wherein saidring flange protrudes from a transverse wall in said housing and isessentially coaxial to said drive shaft and said rotating sleeve.
 8. Theactuating device according to claim 7, further comprising: a retainingsleeve rotationally rigidly connected at the first end to the transversewall of said housing; a guide sleeve adapted to allow longitudinaldisplacement and limit rotational displacement of said actuatingelement; a second spiral spring attached to the second end of saidretaining sleeve and said guide sleeve so as to prevent rotation of saidguide sleeve opposite the feed direction.
 9. The actuating deviceaccording to claim 8, wherein said actuating element is connected to therecirculating ball spindle via a spindle head.
 10. The actuating deviceaccording to claim 9, wherein the spindle head comprises at least oneguide element, protruding radially outwards; and adapted to engage alongitudinal guide disposed on said guide sleeve and running along theregulating direction.
 11. The actuating device according to claim 10,wherein said second spiral spring is drive-connected to a first steppermotor.
 12. The actuating device according to claim 11, wherein the firststepper motor is drive-connected to a clamping sleeve from which a dogprotrudes radially inwards, the dog being connected to one end of thesecond spiral spring.
 13. The actuating device according to claim 12,wherein the clamping sleeve is rotationally supported on an outer sideof the retaining sleeve and an outer side of a ring flange protrudingfrom an inner side of said cover.
 14. The actuating device accordingclaim 13, further comprising a torsion spring arranged between theclamping sleeve and the ring flange, wherein the torsion spring istensed by rotating the clamping sleeve.
 15. The actuating deviceaccording to claim 12, wherein the first stepper motor has a firstgearwheel adapted to engage teeth disposed on one end of the clampingsleeve.
 16. The actuating device according to claim 15, wherein a secondstepper motor is arranged diametrically opposite the first stepper motorand is adapted to drive a second gearwheel adapted to engage the teethon the clamping sleeve.
 17. The actuating device according to claim 16,wherein the teeth are formed by a toothed ring with inner teeth, whereinthe toothed ring is releasably mounted on the end of the clampingsleeve.
 18. The actuating device according to claim 1, wherein the atleast two electric motors can be actuated and controlled independentlyof one another.
 19. The actuating device according to claim 1, whereinthe at least two electric motors are stepper motors.
 20. The actuatingdevice according to claim 1, wherein at least two separate electricalconnections are arranged on the housing cover adjacent to the electricmotors.
 21. The actuating device according to claim 1, wherein bothelectric motors can be operated simultaneously.
 22. The actuating deviceaccording to claim 1, wherein the electric motors are synchronized bysoftware via their motor control devices.
 23. The actuating deviceaccording to claim 1, wherein one electric motor is used as the masterand the other electric motor is used as the slave.
 24. The actuatingdevice according to claim 1, wherein the electric motors are directcurrent motors.
 25. The actuating device according to claim 1, furthercomprising a position sensor assigned to the drive shaft.